Intrauterine Cannibalism in Sharks

Sandtiger Shark (Carcharias taurus)

Two forms of within-the-womb cannibalism are known in sharks. The most
extreme form of intrauterine cannibalism — in which the largest and strongest
embryo actually consumes its lesser womb-mates — is termed "embryophagy"
or, more colorfully, "adelphophagy" — literally "eating
one's brother". It was discovered accidentally in 1948, when a researcher
probing the uteri of a late-term Sandtiger Shark (Carcharias taurus) was
startled by a bite on the hand. To date, adelphophagy is known only in the
Sandtiger. The less extreme and by far more common form of intrauterine
cannibalism — in which developing embryos feed on a steady supply of tiny,
unfertilized eggs — is termed "oophagy" (sometimes called
"oviphagy") — meaning "egg-eating". The earliest
documented case of oophagy dates back to 1907, in the Porbeagle (Lamna nasus).
Both forms of intrauterine cannibalism continue throughout embryonic and fetal
development, so that at birth each pups often has aa conspicuously swollen
abdomen known as a "yolk stomach".

Until quite recently, intrauterine cannibalism was thought to be restricted
to lamnoid sharks. This grisly form of within-the-womb nutrition is now known
from two carcharhinoids and even one orectoloboid. Following is a list of all
sharks in which intrauterine cannibalism has been documented, or for which
exists strong circumstantial evidence: